Structure and method for memory cell array

ABSTRACT

A memory cell array structure includes memory cells arranged in m rows and n columns on a substrate, and n columns of first and second well regions with different conductivity types alternatively arranged along the column direction. Each of the memory cells includes first and second diodes. The first diode formed of a first doped region in the same column is disposed in the first well region. The second diode formed of a second doped region in the same column is disposed in the second well region. A third doped region having the conductivity type of the first well region is disposed in the first well region and is connected to the reset line of the same column. A fourth doped region having the conductivity type of the second well region is disposed in the second well region and is connected to the bit line of the same column.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Application No.201610518865.6, filed on Jul. 4, 2016 with the State IntellectualProperty Office of People's Republic of China, the content of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to semiconductor memory devices. Moreparticularly, embodiments of the present invention provide a memory cellarray structure, an electronic device including the same, and a methodof manufacturing the same.

BACKGROUND OF THE INVENTION

Resistive random access memory (RRAM) devices are widely used inelectronic appliances as nonvolatile memory devices due to their manyadvantages, such as fast read/write access times, a large number oftimes of read/write operations, long data retention time, small unitarea, multi-value storage, and others. The electrical resistance of aresistive random access memory may vary with an applied voltage orcurrent to a bottom electrode, exhibiting a low resistance and a highresistance for storing a logic “0” and a logic “1”.

A resistive random access memory (RRAM) unit generally requires aselector to eliminate the sneak leakage path. An NMOS transistor or a PNdiode is generally used as a RRAM selector, which is referred to as a1T1R or 1D1R structure. The 1T1R structure of the RRAM unit includes atransistor and an RRAM, and the 1D1R structure includes a PN diode andan RRAM. The RRAM selector requires a high SET and RESET current, asmall size, a relatively high breakdown voltage, and low leakagecurrent. However, as technology nodes are reduced to 40 nm and below,the 1T1R and 1D1R structures cannot meet these requirements.

A 1D1R structure of a RAM cell is a unipolar/nonpolar cell, however, aconventional RRAM cell is bipolar, that is, it needs to pass a highforward current to implement the SET operation and a high reversecurrent to implement the RESET operation, however, a diode can onlyprovide a high current in one direction.

Therefore, in order to implement a bipolar RRAM having a high currentand a low leakage current, a 2D1R (including two diodes and one RRAM)structure has been proposed for an RRAM memory cell array. A layoutdesign of the 2D1R RRAM memory cell array in a silicon substrate forminimizing the size of the memory cell array structure is one of thetechnical problems that are currently under study.

BRIEF SUMMARY OF THE INVENTION

In an effort to solve the aforementioned needs, embodiments of thepresent invention provide a memory cell array structure, device andmethod of manufacturing the same to reduce the size of a memory cellarray structure, the sneak current, and increase the switching speed ofthe 2D1R structure while utilizing standard CMOS processes without majormodifications.

Embodiments of the present invention provide a memory cell arraystructure. The memory cell array structure includes a semiconductorsubstrate, a plurality of memory cells arranged in m rows and n columnson the semiconductor substrate, m and n being positive integers, each ofthe memory cells including a first diode, a second diode, and a randomaccess memory component, n columns of first well regions and n columnsof second well regions spaced apart from each other in the semiconductorsubstrate and alternatively disposed along a column direction, the firstwell regions having a first conductivity type, and the second wellregions having a second conductivity type different from the firstconductivity type, m rows of first doped regions in the first wellregions and having the second conductivity type, each one of first dopedregions disposed in one of the first well regions along the columndirection, one of the first doped regions and one of the first wellregions disposed underneath thereof forming a first diode, and m rows ofsecond doped regions in the second well regions and having the firstconductivity type, each one of second doped regions disposed in one ofthe second well regions along the column direction, one of the seconddoped regions and one of the second well regions disposed underneaththereof forming a second diode. The memory cell array structure furtherincludes a plurality of third doping regions having the firstconductivity type of the first well regions, at least one of the thirddoped regions disposed in one of the first well regions, and the thirddoped regions being isolated from adjacent first doped regions, aplurality of fourth doping regions having the second conductivity typeof the second well regions, at least one of the fourth doped regionsdisposed in one of the second well regions, and the fourth doped regionsbeing isolated from adjacent second doped regions, and a plurality ofrandom access memory components disposed on the semiconductor substrate,each of the random access memory components having a bottom electricallyconnected to one of the first doped regions and one of the second dopedregions. The memory cell array structure also includes m rows of wordlines on the random access memory components, spaced apart from eachother and parallel to each other, each of the random access memorycomponents having a top electrically connected to a same word line, ncolumns of reset lines each on third doped region in a same column andelectrically connected to the third doped regions in the same column andunderneath thereof, the rest lines being isolated from each other, and ncolumns of bit lines each on fourth doped regions in a same column andelectrically connected to the fourth doped regions in the same columnand underneath thereof, the bit lines being isolated from each other.

In one embodiment, one of the third doped regions in one of the firstwell regions is disposed at one end of the one of the first wellregions.

In one embodiment, one of the fourth doped regions in one of the secondwell regions is disposed at one end of the one of the second wellregions.

In one embodiment, the third doped regions and the fourth doped regionsare alternatively arranged in the row direction.

In one embodiment, the memory cell array structure further includes adeep trench isolation structure between adjacent first well regions andsecond well regions, the deep trench isolation structure extending alongthe column direction in the semiconductor substrate and having a bottomlower than a bottom of the first well regions and a bottom of the secondwell regions.

In one embodiment, the memory cell array structure further includes ashallow trench isolation structure between adjacent first doped regionsin a same first well region, between adjacent third doped regions andfirst doped regions, between adjacent second doped regions in a samesecond well region, and between the fourth doped regions and the seconddoped regions, the shallow trench isolation structure having a bottomhigher than a bottom of the first well regions and a bottom of thesecond well regions.

In one embodiment, the memory cell array structure further includes anisolation well region having the second conductivity type, the isolationwell region being disposed below the first well regions and the secondwell regions.

In one embodiment, the isolation well region has an upper portionadjacent to a bottom of the first well regions and a bottom of thesecond well regions.

In one embodiment, the n columns of reset lines each extend along thecolumn direction toward an outer edge of the memory cell arraystructure.

In one embodiment, the n columns of bit lines each extend along thecolumn direction toward an outer edge of the memory cell arraystructure.

In one embodiment, the first conductivity type is P-type and the secondconductivity type is N-type; or, the first conductivity type is N-typeand the second conductivity type is P-type.

In one embodiment, the random access memory component is one of aresistive random access memory, a phase-charge random access memory, ora magnetic random access memory.

In one embodiment, the memory cell array structure further includes aninterconnect metal layer disposed on the semiconductor substrate andbelow the random access memory component and electrically connected to abottom of the random access memory component, a first contact hole and asecond contact hole below the interconnect metal layer and isolated fromeach other. The first contact hole is electrically connected between oneof the first doped regions and the interconnect metal layer, and thesecond contact hole is electrically connected between one of the seconddoped regions and the interconnect metal layer.

In one embodiment, the interconnect metal layer is electricallyconnected to different ones of the random access memory components.

In one embodiment, each of the reset lines is electrically connected toa corresponding third doped region disposed underneath thereof through athird contact hole on the semiconductor substrate.

In one embodiment, each of the bit lines is electrically connected to acorresponding fourth doped region disposed underneath thereof through afourth contact hole on the semiconductor substrate.

In one embodiment, the reset lines and the bit lines are parallel toeach other.

In one embodiment, the semiconductor substrate has the firstconductivity type.

In one embodiment, the memory cell array structure further includes anisolation well region having the second conductivity type disposed belowthe first well regions and configured to isolate the first well regionsfrom the semiconductor substrate.

Embodiments of the present invention also provide an electronic deviceincluding the above-described memory cell array structure.

The following description, together with the accompanying drawings, willprovide a better understanding of the nature and advantages of theclaimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a memory cell array structure according to oneembodiment of the present invention;

FIG. 2A illustrate a simplified cross-sectional view of the memory cellarray structure taken along the line X1 of FIG. 1 according to oneembodiment of the present invention;

FIG. 2B illustrate a simplified cross-sectional view of the memory cellarray structure taken along the line X2 of FIG. 1 according to oneembodiment of the present invention;

FIG. 2C illustrate a simplified cross-sectional view of the memory cellarray structure taken along the line Y1 of FIG. 1 according to oneembodiment of the present invention;

FIG. 2D illustrate a simplified cross-sectional view of the memory cellarray structure taken along the line Y2 of FIG. 1 according to oneembodiment of the present invention;

FIG. 3 illustrates a circuit diagram of a memory cell array according toone embodiment of the present invention;

FIG. 4 is a schematic diagram of an electronic device according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention now will be described more fullyhereinafter with reference to the accompanying drawings. The inventionmay, however, be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. The features may not be drawn to scale, some detailsmay be exaggerated relative to other elements for clarity. Like numbersrefer to like elements throughout.

It will be understood that when an element such as a layer, region orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present. Itwill also be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising”, “includes”, and/or “including” when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may beimplemented. The term “upper”, “lower”, “vertical”, “horizontal”,“depth”, “height”, “width”, “top”, “bottom”, etc., is used withreference to the orientation of the Figures being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the term is used for purposes ofillustration and is not limiting. It will be understood that these termsare intended to encompass different orientations of the device inaddition to the orientation depicted in the figures.

It will be understood that, although the terms “first,” “second,”“third,” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another region, layer or section. Thus, a firstelement, component, region, layer or section discussed below could betermed a second element, component, region, layer or section withoutdeparting from the teachings of the present invention.

The term “horizontal” as used in this application is defined as a planeparallel to the conventional plane or surface of a wafer or substrate,regardless of the orientation of the wafer or substrate. The term“vertical” refers to a direction perpendicular to the horizontal asdefined above. Prepositions, such as “on”, “side” (as in “sidewall”),“underneath”, “below”, “above”, “higher”, “lower”, “over” and “under”are defined with respect to the conventional plane or surface being onthe top surface of the wafer or substrate, regardless of the orientationof the wafer or substrate. It will be understood that these terms areintended to encompass different orientations of the device in additionto the orientation depicted in the figures.

The N+ (or n+) layer is highly doped with impurities to a concentrationof at least 10E18(10¹⁸) atoms per cm³ or a dose of at least 10E14 (10¹⁴)atoms per cm². The N− (or n−) layer has a lower doping concentration,but is still an n-type and has an impurity concentration in the range of10E14 (10¹⁴) to 10E15 (10¹⁵) atoms per cm³ or a dose of 10E10 to 10E11(10¹⁰ to 10¹¹) atoms per cm². The P (or p) layer is lightly doped withimpurities to a concentration in the range of 10E14 (10¹⁴) to 10E15(10¹⁵) atoms per cm³ or a dose of 10E10 to 10E11 (10¹⁰ to 10¹¹) atomsper cm². The P+ (or p+) layer is highly doped with impurities to aconcentration of at least 10E18 (10¹⁸) atoms per cm³ or a dose of atleast 10E14 (10¹⁴) atoms per cm².

Embodiments of the invention are described herein with reference tocross-seg tional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention.The thickness of layers and regions in the drawings may be enlargedrelative to other layers and regions for clarity. Additionally,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments of the invention should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a discretechange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofthe invention.

Embodiments of the present invention now will be described more fullyhereinafter with reference to the accompanying drawings, in whichembodiments of the invention are shown. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein.

In order to realize the layout of a 2D1R RRAM cell array in asemiconductor substrate (e.g., silicon substrate) and minimize the sizeof the memory cell array, embodiments of the present invention provide amemory cell array structure comprising a semiconductor substrate, aplurality of memory cells arranged in m rows and n columns on thesemiconductor substrate, where m and n are positive integers. Each ofthe memory cells includes a first diode, a second diode, and a randomaccess memory cell component.

The memory cell array structure also includes n rows of first wellregions and n rows of second well regions each extending along thedirection of the column, the n rows of first and second well regions arealternatively disposed in the semiconductor substrate along thedirection of the row. The first well region has a first conductivitytype, and the second well region has a second conductivity typedifferent from the first conductivity type.

The memory cell array structure also includes a plurality of first dopedregions disposed in the first well regions and having the secondconductivity type. A number m of first doped regions are arranged at afirst predetermined space interval along the column direction in thefirst well regions, one of the first doped regions and one first wellregion below the corresponding one of the first doped regions form afirst diode.

The memory cell array structure also includes a plurality of seconddoped regions disposed in the second well regions and having the firstconductivity type. A number m of second doped regions are arranged at asecond predetermined space interval along the column direction in thefirst well regions, one of the second doped regions and one second wellregion below the corresponding one of the second doped regions form asecond diode.

The memory cell array structure also includes a plurality of randomaccess memory components disposed on the semiconductor substrate, thebottom of each of the random access memory components is electricallyconnected to one of the first doped regions and one of the second dopedregions of a corresponding memory cell.

The memory cell array structure also includes m rows of word linesdisposed above the random access memory components and parallel to eachother, the top of the random access memory components of the memory cellarray disposed on the same row is electrically connected to the sameword line.

The memory cell array structure also includes a plurality of third dopedregions having the same conductivity type as that of the first wellregions, at least one third doped region is provided in one of the firstwell regions, the third doped regions and the adjacent first dopedregions are separated from each other.

The memory cell array structure also includes a plurality of fourthdoped regions having the same conductivity type as that of the secondwell regions, at least one fourth doped region is provided in one of thesecond well regions, the fourth doped regions and adjacent second dopedregions are separated from each other.

The memory cell array structure also includes n columns of reset linesdisposed above the third doped regions, the n columns of reset lines areisolated from each other, each column of the reset lines is electricallyconnected to the corresponding third doped region disposed underneaththereof.

The memory cell array structure also includes n columns of bit linesdisposed above the fourth doped regions, the n columns of bit lines areisolated from each other, each column of the bit lines is electricallyconnected to the corresponding fourth doped region disposed underneaththereof.

The memory cell array structure according to one embodiment of thepresent invention includes m rows and n columns of memory cells formedin a semiconductor substrate. The first well region of the same columnof memory cell serves as the bit line of that column, where the firstwell region of the same memory cell is a lead out to electricallyconnect to a bit line above thereof through the third doped region inthe first well region. The second well region of the same column ofmemory cells is provided as a reset line of the column in which thefourth well region of the second well region disposed in each of thesecond well regions is electrically connected to the reset line. Thememory cell array structure directly uses the first well region and thesecond well region in the semiconductor substrate as the bit line andthe reset line, respectively, to reduce the area of the bit line and thereset line on the semiconductor substrate, so that the size of thememory cell array structure can be significantly reduced while ensuringthe performance of the memory cell array structure.

Embodiment 1

FIG. 1 is a top view of a memory cell array structure 10 according toone embodiment of the present invention. FIG. 2A illustrate a simplifiedcross-sectional view of the memory cell array structure taken along theline X1 of FIG. 1 according to one embodiment of the present invention.FIG. 2B illustrate a simplified cross-sectional view of the memory cellarray structure taken along the line X2 of FIG. 1 according to oneembodiment of the present invention. FIG. 2C illustrate a simplifiedcross-sectional view of the memory cell array structure taken along theline Y1 of FIG. 1 according to one embodiment of the present invention.FIG. 2D illustrate a simplified cross-sectional view of the memory cellarray structure taken along the line Y2 of FIG. 1 according to oneembodiment of the present invention. FIG. 3 illustrates a circuitdiagram of a portion of a memory cell array according to one embodimentof the present invention.

In one embodiment of the present invention, memory cell array structure10 may include a semiconductor substrate 100. Semiconductor substrate100 may be an undoped monocrystalline silicon, a monocrystalline silicondoped with an impurity, a silicon on insulator (SOI), stacked SOI(SSOI), stacked SiGe on insulator (S-SiGeOI), SiGe on insulator(SiGeOI), Ge on insulator (GeOI), or the like. In an exemplaryembodiment, semiconductor substrate 100 is a monocrystalline siliconsubstrate.

In a preferable embodiment, semiconductor substrate 100 may have a firstconductivity type, e.g., the first conductivity type may be P-type orN-type, and a specific selection may be made according to the type ofthe device.

It is to be noted that, in the following disclosure, the firstconductivity type is P-type, the second conductivity type is N-type.Conversely, the first conductivity type is N-type, the secondconductivity type is P-type. Hereinafter, embodiments of the presentinvention will be described in detail with reference to the case wherethe first conductivity type is P-type, and the second conductivity typeis N-type.

Referring to FIG. 1, memory cell array structure 10 may include aplurality of memory cells 11 provided on semiconductor substrate 100 andarranged in m rows and n columns, where m and n are positive integers.

It is to be noted that, in the present invention, the rows and columnsare referred to two mutually perpendicular directions on the surface ofthe semiconductor substrate.

Illustratively, each of the memory cells 11 includes a first diode, asecond diode, and a random access memory component.

Referring to FIGS. 2A through 2D, memory cell array structure 10 mayfurther include n columns of first well regions 102 and n columns ofsecond well regions 103, each of first well regions 102 and each ofsecond well regions extend along the direction of the column, and firstand second well regions 102, 103 are arranged alternatively insemiconductor substrate 102 along the row direction. First well regions102 have a first conductivity type, second well regions 103 have asecond conductivity type. Memory cells 11 are formed on first wellregions 102 and second well regions 103. Illustratively, first wellregions are P-type well regions, and second well regions are N-type wellregions.

In one embodiment, when semiconductor substrate 100 has the firstconductivity type, an isolation well region 101 is provided insemiconductor substrate 100 to isolate semiconductor substrate 100 fromfirst and second well regions 102 and 103. Isolation well region 101 hasthe second conductivity type and is located below first well regions 102and second well regions 103. Preferably, the top portion of isolationwell region 101 is in the proximity of the bottom of first well regions102 and second well regions 103. When semiconductor substrate 100 is aP-type substrate, first well regions 102 are P-type well regions, secondwell regions 103 are N-type well regions, and isolation well region 101is an N-type isolation well region to isolate the first well regionsfrom the semiconductor substrate.

In one embodiment, a deep trench structure 106 is provided betweenadjacent first well regions 102 and second regions 103 to isolate firstwell regions 102 from second regions 103. Deep trench structure 106 hasa length extending along the column direction to completely isolatefirst well regions 102 from second regions 103. Deep trench structure106 is disposed in semiconductor substrate 100 and has an upper surfacethat is slightly higher than the upper surface of semiconductorsubstrate 100, or the an upper surface of deep trench structure 106 isflush with the upper surface of semiconductor substrate 100, and deeptrench structure 106 has a bottom lower than the bottom of first wellregions 102 and second regions 103. When deep trench structure 106 isprovided, the bottom of trench structure 106 is lower than the bottom ofisolation well region 101.

Deep trench structure 106 includes a deep trench filled with a deeptrench isolation material including silicon nitride, silicon oxide, orsilicon oxynitride.

Memory cell array structure 10 may also include a plurality of firstdoped regions 104 disposed in first well regions 102 and having thesecond conductivity type. Each one of first doped regions 104 isdisposed in one of first well regions 102 along the column direction,one of first doped regions 104 and one of first well regions 102 form afirst diode 11 a. First diode 11 a is a constituent element of a memorycell. The number of first doped regions 104 disposed in the first wellregions is determined by the size of the memory cell array, e.g., whenthe memory cell array has m rows and n columns, the number of firstdoped regions 104 disposed in one of first well regions 102 is also m.

By way of example, first well regions 102 are P-type well regions, firstdoped regions 104 are N-type doped regions, which are N-type heavilydoped regions (referred to as N+), i.e., a first doped region 104 andthe corresponding first well region 102 underneath thereof form firstdiode 11 a. The P-type well region is the anode of first diode 11 a, andthe N-type heavily doped region is the cathode of first diode 11 a.Since the plurality of first diodes 11 a share a P-type well region, theanodes of the plurality of first diodes 11 a sharing the P-type wellregion in the same column are electrically connected together.

Memory cell array structure 10 may also include a plurality of seconddoped regions 105 disposed in second well regions 103 and having thefirst conductivity type. Each one of the plurality of second dopedregions 105 are disposed in one of second well regions 103 along thecolumn direction, one of second doped regions 105 and one of second wellregions 103 form a second diode 11 b. Second diode 11 b is a constituentelement of the memory cell. The number of second doped regions 105arranged in the second well region is determined by the size of thememory cell array, e.g., when the memory cell array has m rows and ncolumns, the number of second doped regions 105 disposed in one ofsecond well regions 103 is also m.

Preferably, first doped region 104 and second doped region 105 arearranged in m rows in the row direction, and first doped regions 104 andsecond doped regions 105 are arranged alternatively in the same row.

By way of example, second well regions 103 are N-type well regions,second doped regions 105 are P-type doped regions, which are P-typeheavily doped regions (referred to as P+), i.e., second doped regions105 and corresponding first well regions 102 underneath thereof formsecond diodes 11 b. The P-type well regions are the anodes of seconddiodes 11 b, and the N-type heavily doped regions are the cathodes ofsecond diode 11 b. Since the plurality of second diodes 11 b share anN-type well region, the cathodes of the plurality of first diodes 11 bsharing the N-type well region in the same the column are electricallyconnected together.

Further, first diodes 11 a and second diodes 11 b of adjacent columns inthe same row constitute the elements of the memory cells, and thedifferent memory cells on the same row do not share a common first diode11 a and a common second diode 11 b.

Referring to FIG. 2D, memory cell array structure 10 may further includea plurality of third doping regions 108 having the same conductivitytype as first well regions 102, and at least one of the plurality ofthird doped regions 108 is provided in one of first well regions 102,and third doped regions 108 are isolated from adjacent first dopedregions 104.

One of third doped region 108 in one of first well regions 102 serves asa lead-out region of that one of first well regions 102 to electricallyconnected that one of first well regions 102 to an external circuit.First well regions 102 can be considered as reset lines provided in thesemiconductor substrate.

In a preferred embodiment, third doped regions 108 in one of first wellregions 102 are located at one end of the first well regions in thevicinity of an outer edge of the memory cell array structure.

By way of example, third doped regions 108 are P-type doped regions,preferably a P-type heavily doped region (P+), when first well regions102 are P-type well regions.

Referring to FIG. 2C, memory cell array structure 10 may further includea plurality of fourth doping regions 109 having the same conductivitytype as that of second well regions 103, and at least one of theplurality of fourth doped regions 109 is provided in one of second wellregions 103, and fourth doped regions 109 and adjacent second dopedregions 105 are isolated from each other.

One of fourth doped regions 109 in one of second well regions 103 servesas a lead-out region of that one of second well regions 102 toelectrically connected that one of second well regions 103 to anexternal circuit. Second well regions 103 can be considered as bit linesprovided in the semiconductor substrate.

By way of example, fourth doped regions 109 are N-type doped regions,preferably an N-type heavily doped region (N+), when second well regions103 are N-type well region.

In a preferred embodiment, fourth doped regions 109 in one of secondwell regions 103 are located at one end of second well regions 103 inthe vicinity of an outer edge of the memory cell array structure.

Further, third doped regions 108 and fourth doped regions 109 may beboth in the vicinity of the same outer edge of the memory cell arraystructure, and third doped regions 108 and fourth doped regions 109 arealternatively arranged along the row direction.

In one embodiment, a shallow trench isolation structure 107 is providedbetween adjacent ones of first doped regions 104 located in the samefirst well region 102, between adjacent ones of second doped regions 105located in the same second well region 103, between adjacent third dopedregion 108 and first doped region 104, between adjacent fourth dopedregion 109 and second doped region 107. Shallow trench isolationstructure 107 has a bottom that is higher than the bottom of first wellregion 102 and second well region 103, and lower than the bottom offirst doped region 104, the second doped region 105, third doped region108, and fourth doped region 109. Shallow trench isolation structure 107insulates adjacent first doped region 104, adjacent second doped regions105, adjacent third doped region 108 and first doped region 104, andadjacent fourth doped region 109 and second doped region 105.

Referring back to FIG. 2A, the memory cell array of the presentinvention may further include a plurality of random aces memorycomponents 112 disposed on semiconductor substrate 100 and having abottom electrically connected to first doped region 104 and second dopedregion 105 of the memory cell.

In one embodiment, still referring to FIG. 2A, an interconnect metallayer 111 is disposed on semiconductor substrate 100 under each one ofthe plurality of random aces memory components 112. A first contact hole1101 and a second contact hole 1102 are disposed below interconnectmetal layer 111, first contact hole 1101 is electrically connected tofirst doped region 104 and interconnect metal layer 111, second contacthole 1102 is electrically connected to second doped region 105 andinterconnect metal layer 111, and interconnect metal layer 111 iselectrically connected to the bottom of the random access memorycomponents 112.

Further, interconnect metal layer 111 is electrically connected todifferent ones of the random access memory components 112 that areinsulated from each other.

The memory cell array of the present invention may further include mrows of word lines 113 disposed above the random access memorycomponents 112 and parallel to each other. The random access memorycomponents 112 disposed in the same row have the top that is connectedto the same word line 113, i.e., each row of the memory cellscorresponds to a row of word lines 113, the memory cells of randomaccess memory components 112 disposed in a same row have the topelectrically connected to a word line 113 of the corresponding row, eachword line 113 extends along the row direction.

Word lines 113 may include any suitable conductive material, such as ametal material or a semiconductor material. The metal material mayinclude copper, aluminum, or the like.

By way of example, random aces memory components 112 may be any type ofrandom access memory known to those of skill in the art. For example,random aces memory components 112 may be a resistive random accessmemory (RRAM), a phase change random access memory (PCRAM), or amagnetic random access memory (MRAM).

In a preferred embodiment, random aces memory components 112 is aresistive random access memory.

A resistive random access memory may use the variable resistancecharacteristics of the transition metal oxide (e.g., the resistancevalue varies with voltage) to store data.

An RRAM has two or more states with different resistance values, whichcorrespond to different digital values. By applying a predeterminedvoltage or current to the RRAM, the RRAM switches from one state toanother. For example, the RRAM has a relatively high resistance value(referred to as a “high-resistance state”) and a relatively low state(referred to as a “low-resistance state”). By applying a predeterminedvoltage or current to the electrode, the RRAM can switch from ahigh-resistance state to a low-resistance state, or from alow-resistance state to a high-resistance state.

In one embodiment, the resistive random access memory may include abottom electrode disposed on interconnect metal layer 111, a resistivematerial layer disposed on the bottom electrode, and a top electrodedisposed on the resistive material layer. The bottom electrode iselectrically connected to interconnect meta layer 111, the top electrodeis electrically connected to a word line 113, and further, the bottomelectrode can be in direct contact with interconnect metal layer 111 toobtain an electrical connection.

The bottom electrode may be made of gold (Au), platinum (Pt), ruthenium(Ru), iridium (Ir), titanium (Ti), aluminum (Al), copper (Cu), tantalum(Ta), tungsten (W), iridium-tantalum (Ir-Ta) alloy, or indium tin oxide(ITO). The bottom electrode may also be made of oxide, nitride,fluoride, carbide, boride, or silicide, such as TaN, TiN, TiAlN, TiW, ora combination thereof. In one embodiment, the bottom electrode includesa tantalum nitride layer and a titanium nitride layer.

The resistive material layer is formed on the bottom electrode and indirect contact with the bottom electrode. The resistive material layerhas a thickness between about 20 nm and about 100 nm. The resistivematerial layer may include an oxide of one or more of Ta, Ti, Ni, Co,Hf, Ru, Zr, Zn, Fe, Sn, Al, Cu, Ag, Mo, and Cr. In some embodiments,silicon may be included in the resistive material layer to form thecomposite material. In some embodiments, the resistive material layermay include hafnium oxide and/or zirconium oxide.

A protective layer may be selectively provided on the resistive materiallayer. In various embodiments, the protective layer is a metal, such astitanium, hafnium, platinum, and tantalum. The protective layer has athickness between about 20 angstroms and about 150 angstroms, preferablybetween about 40 angstroms and about 80 angstroms.

The top electrode is provided on the resistive material layer or theoptional protective layer. The top electrode may be made of gold (Au),platinum (Pt), ruthenium (Ru), iridium (Ir), titanium (Ti), aluminum(Al), copper (Cu), tantalum (Ta), tungsten (W), iridium-tantalum (Ir-Ta)alloy, or indium tin oxide (ITO). The top electrode may also be made ofoxide, nitride, fluoride, carbide, boride, or silicide, such as TaN,TiN, TiAlN, TiW, or a combination thereof. The top electrode has athickness between about 100 nm and about 500 nm.

The memory cell array of the present invention may further include ncolumns of reset lines 114, each of reset lines 114 is disposed on acolumn of third doped region 108, the reset lines are insulated fromeach other and are electrically connected to corresponding third dopedregions 108 underneath thereof.

Further, each of reset lines 114 extends along the column directiontoward an outer edge of the memory cell array structure, the outer edgeis the edge in the vicinity of third doped region 108.

By way of example, each of reset lines 114 is electrically connected tothird doped region 108 underneath thereof through third contact hole1103 disposed on semiconductor substrate 100.

The memory cell array of the present invention may further include ncolumns of bit lines 115, each of bit lines 115 is disposed on a columnof fourth doped region 109, the bit lines are insulated from each otherand are electrically connected to corresponding fourth doped regions 109underneath thereof.

In one embodiment, each of bit lines 115 is electrically connected tofourth doped region 108 below through fourth contact hole 1104 disposedon semiconductor substrate 100.

Further, each of bit lines 115 extends along the column direction towardan outer edge of the memory cell array structure, the outer edge is theedge of fourth doped region 109.

Further, reset lines 114 and bit lines 115 are parallel to each other.

Comparing with bit lines and reset lines extending in the direction ofthe entire column in a conventional design, reset lines 114 and bitlines 115 according to embodiments of the present invention only requireto extend a small length at the edge of the memory cell array structureto obtain the same function with a reduced area required for the resetlines and bit lines.

It is to be noted that first contact hole 1101, second contact hole1102, third contact hole 1103, and fourth contact hole 1104 describedabove may be any conductive contact holes. In an example embodiment, thecontact holes may be made of copper, aluminum, or tungsten, or the like.An interconnect metal structure, e.g., copper interconnect metalstructure, may be used instead of first contact hole 1101, secondcontact hole 1102, third contact hole 1103, and fourth contact hole 1104to implement the electrical connection of the diodes and reset lines114, bit lines 115, or interconnect metal layer 111 disposed on thediodes.

It is to be noted that reset lines 114, bit lines 115, or interconnectmetal layer 111 may be formed on the same plane, that is, reset lines114, bit lines 115, or interconnect metal layer 111 may be formed with asame conductive layer using a lithography process and an etchingprocess. The same conductive layer can include any suitable conductivematerial, such as a metal material or a semiconductor material. Themetal material may include, but not limited to, copper (Cu), aluminum(Al), or the like. The semiconductor material may include, but notlimited to, doped or undoped polysilicon.

It is to be noted that the memory cell array of the present inventionmay further include other components or layer structures, e.g., amultilayer dielectric layer may be formed in the interlayer dielectriclayer, that may include, for example, SiO₂, fluorocarbon (CF),carbon-doped silicon oxide (SiOC), or a silicon carbon nitride (SiCN).Alternatively, the dielectric layer may include an SiCN layer on afluorocarbon (CF) layer. Or, the dielectric layer may includefluorocarbon containing fluorine (F) and carbon (C) as the maincomponents, the fluorocarbon may include an amorphous (non-crystalline)structure. Or, the dielectric layer may include a porous structure suchas carbon doped silicon oxide (SiOC).

FIG. 3 is a circuit diagram of a memory cell array according to oneembodiment of the present invention. The circuit diagram is anequivalent circuit diagram of the memory cell array structure of FIG. 1.By way of example, memory cell array structure according to the presentinvention may include m rows and n columns of memory cells 11, each ofmemory cells 11 includes a first diode 11 a, a second diode 11 b, and arandom access memory component 113. First diode 11 a and random accessmemory component 113 are connected in series between a reset line (RL)and a word line (WL), a current flowing through first diode 11 a andrandom access memory component 113 forms a reset path. Second diode 11 band random access memory component 113 are connected in series between aword line (WL) and a bit line (BL), a current flowing through seconddiode 11 b and random access memory component 113 forms a set path.

Referring to FIG. 3, the cathode of first diode 11 a and the anode ofsecond diode 11 b in each of memory cells 11 are electrically connectedto one end of random access memory component 113, the cathodes of seconddiodes 11 b of memory cells 11 disposed in the same column areelectrically connected to the bit line BL of that column. From left toright, the cathodes of second diodes 11 b of the three memory cells 11in the (n-1)th column are electrically connected to the bit line BLn-1of that column in which they are located. The cathodes of second diodes11 b of the three memory cells 11 in the n-th column are electricallyconnected to the bit line BLn of that column in which they are located.The cathodes of second diodes 11 b of the three memory cells 11 in the(n+1)th column are electrically connected to the bit line BLn+1 of thatcolumn in which they are located, and so forth.

Further, from left to right, the anodes of first diodes 11 a of memorycells 11 disposed in the same (n-1)th column are electronicallyconnected to the reset line RLn-1 of that column. The anodes of firstdiodes 11 a of memory cells 11 disposed in the same (n)th column areelectronically connected to the reset line RLn of that column. T anodesof first diodes 11 a of memory cells 11 disposed in the same (n+1)thcolumn are electronically connected to the reset line RLn+1 of thatcolumn, and so forth.

Further, the other end of random access memory component 113 of memorycells 11 in the same row is electrically connected to the word line WL.As shown in FIG. 3, from top to bottom, the other ends of random accessmemory cells 11 of the (n-1)th row are electrically connected to theword line WLn-1 of that row. The other ends of random access memorycells 11 of the (n)th row are electrically connected to the word lineWLn of that row. The other ends of random access memory cells 11 of the(n+1)th row are electrically connected to the word line WLn+1 of thatrow, and so forth.

The number m and n can be any positive integers. Although only a portionof the memory cell array is shown in FIG. 3, one of skill in the artwill appreciate that other sizes of memory cell array structures areequally within the scope of the present invention. For the sake ofsimplicity, only one memory cell 11 is labeled, it is howevercontemplated that other memory cells 11 also include a first diode 11 a,a second diode 11 b, and a random access memory component 113.

Specifically, the operation of the memory cell array according to thepresent invention is shown in the following Table:

selected unselected Word line Bit line Reset line Word line Bit lineReset line SET Vset 0V floating floating floating floating RESET 0Vfloating Vreset floating floating 0V Read Vread 0V floating floatingfloating floating

The memory cell array of the present invention operates in a mannerthat, when the memory cell array is selected, the word line is connectedto a set voltage (Vset), the bit line is connected to a low voltage(e.g., 0V), the reset line is in a floating state, a current flowingfrom the word line through second diode 11 b and random access memorycomponent 113 to the bit line performs a SET operation. When the wordline is connected to a low voltage (e.g., 0V), the bit line is in afloating state, the reset line is connected to a reset voltage (Vreset),a current flowing from first diode 11 a and random access memorycomponent 113 to the word line performs a RESET operation. When the wordline is connected to a read voltage (Vread), the bit line is connectedto a low voltage (e.g., 0V), the reset line is in a floating state, acurrent flowing from the word line through second diode 11 b and randomaccess memory component 113 to the bit line performs a Read operation.

When the memory cell array is unselected, when a SET operation isperformed, the word line, the bit line and the reset line are in afloating state. When a RESET operation is performed, the word line andthe bit line are in a floating state, the reset line is connected to alow voltage (e.g., 0V). When a read operation is performed, the wordline, the bit line and the reset line are in a floating state.

Thus, the memory cell array structure according to embodiments of thepresent invention includes a plurality of memory cells, each having twodiodes and a resistive random access memory component. The memory cellarray structure can realize the requirement of bipolar RRAM, with one ofthe diodes being used to implement the read operation and the setoperation, and the other diode being used to implement the resetoperation.

In summary, the memory cell array structure according to embodiments ofthe present invention includes m rows and n columns of memory cellsformed in a semiconductor substrate, each of the memory cells having apitch of 4F extending along the word line direction, and a pitch of 2Fextending along the bit line direction, so that each memory cell has asize of 4F×2F=8F², where F is the feature size of the device. Thus, a2D1R memory cell array structure is implemented on a silicon substrate.

In the memory cell array structure according to embodiments of thepresent invention, the first well region of memory cells disposed in asame column serves as the bit line of those memory cells in the samecolumn, the third well region disposed in each of the first well regionsis provided as a conductive lead line to electrically connect to a bitline above a corresponding first well region. A second well region ofmemory cells disposed in the same column is provided as a reset line ofthe memory cells in the same column, the fourth doped region disposed ineach of the second well region is provided as a conductive lead line toelectrically connect to a reset line above the second well region. Inaccordance with the present invention, the memory cell array structuredirectly uses the first well region and the second well region disposedin the substrate as the bit line and the reset line, respectively, toreduce the area of the bit line and the reset line on the semiconductorsubstrate, thereby significantly reducing the size of the memory cellarray structure.

Embodiment 2

Embodiments of the present invention also provide an electronic deviceincluding the memory cell array structure described in the sectionsabove.

An electronic device, in accordance with a second embodiment of thepresent invention, may include the semiconductor device as described inthe first embodiment, which may be manufactured according to the memorycell array structure described in the first embodiment. Because thesemiconductor device according to the embodiment described above has areduced size of memory cell array structure, the electronic deviceaccording to this embodiment also includes the advantages describedabove.

The electronic device may be a mobile phone, tablet PC, laptop, netbook,game console, DVD player, GPS device, voice recorder, MP3, MP4, PSP, orother electronic products.

FIG. 4 is an example of a mobile phone handset 400. Mobile phone handset400 may include a housing 401, a display portion 402, an operationbutton 403, an external connection port 404, a speaker 405, a microphone406, and a semiconductor device, and others.

The semiconductor device includes a memory cell array structure asdescribed in embodiment 1. The memory cell array structure may include asemiconductor substrate, a plurality of memory cells arranged in m rowsand n columns on the semiconductor substrate, where m and n are positiveintegers. Each of the plurality of memory cells includes a first diode,a second diode, and a random access memory component. The memory cellarray structure may further include n columns of first well regions andn columns of second well regions, each of the first and second wellregions extends along the column direction and alternatively disposed inthe semiconductor substrate along the row direction. The first wellregions have a first conductivity type, and the second well regions havea second conductivity type different from the first conductivity type.

The memory cell array structure may further include a plurality (e.g., mrows) of first doped regions in the first well regions and having thesecond conductivity type, each one of the first doped regions isdisposed in one of the first well regions along the column direction,one of the first doped regions and one first well region underneath thecorresponding one of the first doped regions form a first diode.

The memory cell array structure may further include a plurality (e.g., mrows) of second doped regions in the second well regions and having thefirst conductivity type, each one of the second doped regions isdisposed in one of the second well regions along the column direction,one of the second doped regions and one second well region underneaththe corresponding one of the second doped regions form a second diode.

The memory cell array structure may further include a plurality of thirddoped regions having the same conductivity type as the first wellregion, at least one of the third doped regions being provided in one ofthe first well regions, and the third doped regions are insulated fromadjacent first doped regions.

The memory cell array structure may further include a plurality offourth doped regions having the same conductivity type as the secondwell region, at least one of the fourth doped regions being provided inone of the second well regions, and the fourth doped regions areinsulated from adjacent second doped regions.

The memory cell array structure may further include a plurality ofrandom access memory components disposed on the semiconductor substrate,each of the random access memory components having a bottom that iselectrically connected to one of the first doped regions and one of thesecond doped region of a corresponding memory cell.

The memory cell array structure may further include m rows of word linesdisposed on the random access memory components and spaced apart fromeach other and parallel to each other, the random access memorycomponents of the memory cells located in the same row have a topelectrically connected to the same word line.

The memory cell array structure may further include n columns of resetlines disposed on third doped regions of a same column, the reset linesare insulated from each other, and each one of the reset lines iselectrically connected to a third doped region below the correspondingone of the reset lines of the same column.

The memory cell array structure may further include n columns of bitlines disposed on fourth doped regions of a same column, the bit linesare insulated from each other, and each one of the bit lines iselectrically connected to a fourth doped region below the correspondingone of the bit lines of the same column.

The memory cell array structure according to embodiments of the presentinvention includes m rows and n columns of memory cells formed in asemiconductor substrate, each of the memory cells having a pitch of 4Fextending along the word line direction (row direction), and a pitch of2F extending along the bit line direction (column direction), so thateach memory cell has a size of 4F×2F=8F², where F is the feature size ofthe device. Thus, a 2D1R memory cell array structure is implemented on asilicon substrate.

Further, the memory cell array structure according to embodiments of thepresent invention includes a first well region of memory cells disposedin a same column and configured to be the bit line of those memory cellsin the same column, the third well region disposed in one of the firstwell regions is provided as a conductive lead-out line to electricallyconnect to a bit line above a corresponding first well region. A secondwell region of memory cells disposed in a same column is provided as areset line of the memory cells in the same column, the fourth dopedregion disposed in one of the second well region is provided as aconductive lead-out line to electrically connect to a reset line abovethe corresponding second well region. In accordance with the presentinvention, the memory cell array structure directly uses the first wellregions and the second well regions disposed in the substrate as the bitlines and the reset lines, respectively, to reduce the area of the bitlines and the reset lines on the semiconductor substrate, therebysignificantly reducing the size of the memory cell array structure.

Because the electronic device of the present invention includes theabove-described memory cell array structure, the electronic device alsohas the advantages of the memory cell array structure described above.

The preferred embodiments of the present invention have been describedfor illustrative purposes, and those skilled in the art will appreciatethat various modifications, additions and substitutions are possible,without departing from the scope and spirit of the invention asdisclosed in the appended claims.

What is claimed is:
 1. A memory cell array structure, comprising: asemiconductor substrate; a plurality of memory cells arranged in m rowsand n columns on the semiconductor substrate, m and n being positiveintegers, each of the memory cells including a first diode, a seconddiode, and a random access memory component; n columns of first wellregions and n columns of second well regions spaced apart from eachother in the semiconductor substrate and alternatively disposed along acolumn direction, the first well regions having a first conductivitytype, and the second well regions having a second conductivity typedifferent from the first conductivity type; m rows of first dopedregions in the first well regions and having the second conductivitytype, each one of first doped regions disposed in one of the first wellregions along the column direction, one of the first doped regions andone of the first well regions disposed underneath thereof forming afirst diode; m rows of second doped regions in the second well regionsand having the first conductivity type, each one of second doped regionsdisposed in one of the second well regions along the column direction,one of the second doped regions and one of the second well regionsdisposed underneath thereof forming a second diode; a plurality of thirddoping regions having the first conductivity type of the first wellregions, at least one of the third doped regions disposed in one of thefirst well regions, and the third doped regions being isolated fromadjacent first doped regions; a plurality of fourth doping regionshaving the second conductivity type of the second well regions, at leastone of the fourth doped regions disposed in one of the second wellregions, and the fourth doped regions being isolated from adjacentsecond doped regions; a plurality of random access memory componentsdisposed on the semiconductor substrate, each of the random accessmemory components having a bottom electrically connected to one of thefirst doped regions and one of the second doped regions; m rows of wordlines on the random access memory components, spaced apart from eachother and parallel to each other, each of the random access memorycomponents having a top electrically connected to a same word line; ncolumns of reset lines each on third doped region in a same column andelectrically connected to the third doped regions in the same column andunderneath thereof, the rest lines being isolated from each other; ncolumns of bit lines each on fourth doped regions in a same column andelectrically connected to the fourth doped regions in the same columnand underneath thereof, the bit lines being isolated from each other. 2.The memory cell array structure of claim 1, wherein one of the thirddoped regions in one of the first well regions is disposed at one end ofthe one of the first well regions.
 3. The memory cell array structure ofclaim 2, wherein one of the fourth doped regions in one of the secondwell regions is disposed at one end of the one of the second wellregions.
 4. The memory cell array structure of claim 3, wherein thethird doped regions and the fourth doped regions are alternativelyarranged in the row direction.
 5. The memory cell array structure ofclaim 1, further comprising a deep trench isolation structure betweenadjacent first well regions and second well regions, the deep trenchisolation structure extending along the column direction in thesemiconductor substrate and having a bottom lower than a bottom of thefirst well regions and a bottom of the second well regions.
 6. Thememory cell array structure of claim 1, further comprising a shallowtrench isolation structure between adjacent first doped regions in asame first well region, between adjacent third doped regions and firstdoped regions, between adjacent second doped regions in a same secondwell region, and between the fourth doped regions and the second dopedregions, the shallow trench isolation structure having a bottom higherthan a bottom of the first well regions and a bottom of the second wellregions.
 7. The memory cell array structure of claim 1, furthercomprising an isolation well region having the second conductivity type,the isolation well region being disposed below the first well regionsand the second well regions.
 8. The memory cell array structure of claim7, wherein the isolation well region has an upper portion adjacent to abottom of the first well regions and a bottom of the second wellregions.
 9. The memory cell array structure of claim 1, wherein thencolumns of reset lines each extend along the column direction toward anouter edge of the memory cell array structure.
 10. The memory cell arraystructure of claim 1, wherein the n columns of bit lines each extendalong the column direction toward an outer edge of the memory cell arraystructure.
 11. The memory cell array structure of claim 1, wherein thefirst conductivity type is P-type and the second conductivity type isN-type; or, the first conductivity type is N-type and the secondconductivity type is P-type.
 12. The memory cell array structure ofclaim 1, wherein the random access memory component is one of aresistive random access memory, a phase-charge random access memory, ora magnetic random access memory.
 13. The memory cell array structure ofclaim 1, further comprising: an interconnect metal layer disposed on thesemiconductor substrate and below the random access memory component andelectrically connected to a bottom of the random access memorycomponent; a first contact hole and a second contact hole below theinterconnect metal layer and isolated from each other, the first contacthole being electrically connected between one of the first doped regionsand the interconnect metal layer, the second contact hole beingelectrically connected between one of the second doped regions and theinterconnect metal layer.
 14. The memory cell array structure of claim13, wherein the interconnect metal layer is electrically connected todifferent ones of the random access memory components.
 15. The memorycell array structure of claim 1, wherein each of the reset lines iselectrically connected to a corresponding third doped region disposedunderneath thereof through a third contact hole on the semiconductorsubstrate.
 16. The memory cell array structure of claim 1, wherein eachof the bit lines is electrically connected to a corresponding fourthdoped region disposed underneath thereof through a fourth contact holeon the semiconductor substrate.
 17. The memory cell array structure ofclaim 1, wherein the reset lines and the bit lines are parallel to eachother.
 18. The memory cell array structure of claim 1, wherein thesemiconductor substrate has the first conductivity type.
 19. The memorycell array structure of claim 1, further comprising an isolation wellregion having the second conductivity type disposed below the first wellregions and configured to isolate the first well regions from thesemiconductor substrate.
 20. An electronic device comprising a memorycell array structure, the memory cell array structure comprising: asemiconductor substrate; a plurality of memory cells arranged in m rowsand n columns on the semiconductor substrate, m and n being positiveintegers, each of the memory cells including a first diode, a seconddiode, and a random access memory component; n columns of first wellregions and n columns of second well regions spaced apart from eachother in the semiconductor substrate and alternatively disposed along acolumn direction, the first well regions having a first conductivitytype, and the second well regions having a second conductivity typedifferent from the first conductivity type; m rows of first dopedregions in the first well regions and having the second conductivitytype, each one of first doped regions disposed in one of the first wellregions along the column direction, one of the first doped regions andone of the first well regions disposed underneath thereof forming afirst diode; m rows of second doped regions in the second well regionsand having the first conductivity type, each one of second doped regionsdisposed in one of the second well regions along the column direction,one of the second doped regions and one of the second well regionsdisposed underneath thereof forming a second diode; a plurality of thirddoping regions having the first conductivity type of the first wellregions, at least one of the third doped regions disposed in one of thefirst well regions, and the third doped regions being isolated fromadjacent first doped regions; a plurality of fourth doping regionshaving the second conductivity type of the second well regions, at leastone of the fourth doped regions disposed in one of the second wellregions, and the fourth doped regions being isolated from adjacentsecond doped regions; a plurality of random access memory componentsdisposed on the semiconductor substrate, each of the random accessmemory components having a bottom electrically connected to one of thefirst doped regions and one of the second doped regions; m rows of wordlines on the random access memory components, spaced apart from eachother and parallel to each other, each of the random access memorycomponents having a top electrically connected to a same word line; ncolumns of reset lines each on third doped region in a same column andelectrically connected to the third doped regions in the same column andunderneath thereof, the rest lines being isolated from each other; ncolumns of bit lines each on fourth doped regions in a same column andelectrically connected to the fourth doped regions in the same columnand underneath thereof, the bit lines being isolated from each other.